There are in general two basic systems of glazing aluminum or vinyl window sash.
The first system involves the use of a generally U-shaped flexible channel which is either separately mounted on the edges of the glass pane or is integral with the sash. In either situation, the glass pane is secured to the channel by a friction fit, caulking or a combination of both. The majority of sash constructions use a separate flexible U-channel or a dual durometer sash having an integral U-shaped channel with flexible ribs projecting inwardly or some sort of retainer bead or the like.
The second system of glazing such sash involves "drop-in" glass where a glass pane is inserted into the open "light" so that all its bare edges abut a flange or glazing leg which extends inwardly from the sash or mainframe. This is the same system used for many years in the glazing of wooden sash. The chief problem resulting from use of the "drop-in" method of glazing aluminum and vinyl sash, where caulking or glue is used as the main retention agent for the glass, is the difficulty in reglazing if the glass is broken. One reason is the problem in removing some types of glazing retainer beads.
Another almost universal problem results from dropping the glass directly onto an adhesive on the flange or glazing leg of an aluminum or vinyl sash. Whether the adhesive used in securing the glass pane to the sash is the gunnable type or a tape type both adhesives are intended to adhere to the aluminum or vinyl and to the glass. This of course, makes removal of broken glass and its replacement very difficult as reglazing requires not only the disposal of the broken glass but removal of the original adhesive remaining on the glazing leg before applying the new adhesive and glass.
U.S. Pat. No. 3,344,573 addresses this problem to some extent by providing a glazing strip that is first adhesively fastened to a glass pane. The pane is thereafter dropped into the open light without securing the glazing strip to the sash. Thereafter, the pane with glazing strip attached is secured to the sash by a glazing bead applied to the outside surface of the glass and the sash. A major problem of this system is that it still requires the use of a glazing bead which, when the glass breaks, creates problems in removal of the broken glass. In addition, the glazing bead involves an extra element which drives up the overall cost of the sash. Further, the device of U.S. Pat. No. 3,344,573 cannot be reused if the pane to which it is attached is broken.